This invention relates to a light transmitting glass-ceramics comprising fine crystals of calcium phosphate uniformly dispersed in a SiO.sub.2 -Al.sub.2 O.sub.3 -ZrO.sub.2 base glass matrix.
Calcium phosphate glass-ceramics are attracting increasing interest particularly as biomaterials. Many of calcium phosphate glass-ceramics proposed until now have used glass compositions high in the content of P.sub.2 O.sub.5. However, a glass composition containing a large amount of P.sub.2 O.sub.5 is not easy to glassify, and in heat-treating the glass for crystallizing calcium phosphate it is often that growth of crystal grains becomes nonuniform by reason of significant development of phase separation of the glass. As a consequence mechanical strength of the obtained glass-ceramics is not so high as expected.
When the content of alkali in calcium phosphate glass-ceramics is increased, a question arises in biocompatability of the glass-ceramics because transfer of the alkali into the living body might disturb a physiological balance. Besides, the increased alkali adversely affects the heat resistance, electrical insulation resistance and chemical resistance of the glass-ceramics.
JP-A No. 61-141641 and JP-A No. 61-158841 relate to calcium phosphate glass-ceramics and show adding a small amount of ZrO.sub.2 as an optical nucleating agent to a SiO.sub.2 -Al.sub.2 O.sub.3 -P.sub.2 O.sub.5 -CaO-MgO base or SiO.sub.2 -P.sub.2 O.sub.5 -CaO base glass composition. Including these ZrO.sub.2 -containing glass-ceramics none of calcium phosphate glass-ceramics proposed until now, as long as we know, allow visible light to pass therethrough.